Spark-plug.



F. L. SESSIONS.

SPARK PLUG.

APPLICATION FILED MAY 8. ISIS.

1,228,487. Patented June 5, 1917.

ma., WCM/MMM SPARK-FLUG.

Specification of Letters Patent.

patented .rane 5, mit.

Application led May 8, 1915. Serial No. 26,763.

To all whom t may concern.'

Be it known that l, FRANK L. SESSIONS, a citizen of the United States, residing at Lakewood, in the county of Cuyahoga and State of Ohio, have inventedcertain new and useful Improvements in Spark-Plugs, of which the following is a specification.

My invention relates to improvements in electric spark plugs, such as are used for igniting explosive mixtures of fuel and air in internal combustion engines, and has for its object the provision of a simple, cheap, and readily manufactured spark plug having a ground terminal combined with a packing washer for the porcelain or other insulating material which supports the insulated electrode, and possessing advantages over existing types of spark plugs which will be apparent from these specifications.

A further object of my invention is the provision of means whereby the ground terminal may be -readily and quickly re moved from the supporting metal shell for inspection and cleaning, and replaced with assurance that the length of the spark gap has not been altered.

A further object of my invention is to provide a spark plug, from which the porcelain or other insulating material which supports the insulated electrode may be easily withdrawn and cleaned and again returned to itsv place without changing the length of the spark gap. Y

l have found that the insulated electrode frequently becomes short crcuited tothe metal shell surrounding it by a thin but continuous layer of carbon extending over the sur-face of the insulating material from the insulated electrode to the metalshell which is screwed into the wall of the cylinder or combustion chamber. In most instances this layer of carbon can be easily wiped or scraped off from the insulation and the spark plugl is thereby made perfectly operative again. Existing spark plugs are so constructed that either it is diflicult or impossible to remove the insulation for cleaning, or when it has been so removed, cleaned, and replaced, the length of the spark gap is not the same as it was before. Some of the present forms of spark plugs are designed so that the porcelain members may be removed and cleaned without removing the metal shell from the cylinder, but in those spark plugs with which l am familiar it is impossible to examine the normally grounded sparking point without removing the above mentioned metal shell; or, auxiliary metal shells are used which are secured to the insulation in a permanent manner, making cleaning, inspection and packlng very difficult. In such spark plugs, when the porcelain is again returned to its seat, especially if a new packing washer be employed to make. a fluid tight joint, the length of the spark gap is frequently changed, making it necessary to adjust it in order to secure proper ignition. Other spark plugs have been designed to overcome some of these objections, but they are composed of many parts which are difficult to manipulate.

By the use of my improvements, the inspection and care of this important adjunct tothe internal combustion engine is readily given by even unskilled persons, and much time trouble and expense are 'thereby saved. By my construction it is possible to make the combined ground terminal and packing washers perfectly interchangeable, so that the replacement of an old by a new one does not materially alter the length of the spark gap. Thelength of the spark gap of my improved spark plug may, however, be adjusted as readily as that in any of the existing types with which I am familiar.

The particular means and their functions employed in carrying out the objects of my invention are fully described in these lspecilcations and claims and shown in the ac-v companying drawings in which Figure 1 is a longitudinal section through a preferred form of spark plug embodying my improvements; Fig. 2 is a plan, and Fig. Bris a longitudinal section of the combined ground terminal and packing washer used in the spark plug shown in Fig. l; Fig. 4 is a longitudinal section through another form of spark plug embodying a modification of my improvements; Figs. 5 and 6, are respectively plan and longitudinal section of the ground terminal and packing washer shown in Fig. 4: Figs. 7 and 8 are respectively plan and longitudinal section of a different form of my improved combination ground terminal and packing washer in which there are shown variations in 'the sparking point and packing washer; Fig. 9 is a longitudinal section of a spark plug using the form of ground terminal and packing washer combustion engine cylinder.

cap threaded internally and screwed ontoy shown in Figs. 'i' and 8, together with an I ways, either by bending in a portion of the metal wall of the ground terminal; or by attaching to it a wire of suitable material; or by simply leaving the wall of the ground terminal in its circular cross sectional form with an open bottom end, and bringing theinslated sparking point into proper proximity to form 'the desired length of spark gap.

Referring' to the drawings, 1 represents the exteriormetal shell or body of a spark plug, having its lower end threaded and screwed into the metal wall, 2, of an internal 3 is a metal the correspondingly externally threaded upper end oic the shell, 1. rlhe cap, 3, is provided with an inturned shoulder or flange, il, for clamping the insulation, 5, preferably made of porcelain, firmly in place. 6 represents the combined ground terminal and packing washer. As shown in Figs. 1, 2, and ,3, it has the form of a holilow, thin walled metal cylinder or thimble, having a practically straight body portion, v"4', a rounded bottom, 8, and an outwardly turned flange, 9., at the top end. The flange, 9, is shown turned over a cushioning washer, 10, or' asbestos or other yielding material suitable for the purpose, in order that the comparatively thin and soft metal of the flange, 9, may con-form to any slight irregularities in the surfaces of the insulation, 5, and the metal shell, 1, between which the flange, 9, is clamped so as to make duid tight joints therewith. c

lt will be observed that asidefrom the slight yielding ot the metal of the top surface of the llange, 9, as it is clamped in place between the insulation, 5, and the shell 1, there will be no change in the length oic the spark gap due to the yielding of the cushioning washer, as both the insulated and the grounded spark points'will move in unison in response to such yielding or the cushioning washer, as will be apparent from the urther description of these parts.

l prefer to make the body portion, 7, of theground terminal, 6, larger in diameter than the insulation which it surrounds, in order that any carbon which may accumulate on their opposed surfaces may not form a short circuit between the electrodes. l' have found that the length or time a spark.

plug may be operated without cleaning is ineens? about proportional to the distance between the insulated electrode and the normally grounded electrode as measured on the surrace of the intervening insulation. lt is therefore desirable to leave a clearance space between Athe insulation and the grounded electrode So that carbon deposits may not effect a virtual shortening of this surface distance. rChe ground terminal, 6, may be made to lit somewhat loosely in the bore of the shell, l, as electrical contact between thesemembers is insured by the clamping of the flange, 9, against the end of shell, l.

11 represents the sparking terminal of the insulated electrode,12. rlhis insulated electrode'passes through andis sealed into the insulation, 5, in the usual manner, and is provided at its protruding outer end with a threaded portion 12a, on which are the customary means such as the nut, 13, and jam nut, 14C, for making connections to the electric circuit. 15 is a metal cushioning washer between the insulation, 5, and the shoulder, Ll, of the cap, 3. When a modilied form of my combined ground terminal and packing washer, to be presently described, is used, the washer, 15, may be dispensed with.

16 is a sparking point upon the ground terminal or electrode, 6. As shown in Figs. 1, 2, and 3, it is Jformed by making a sharp inwardly projecting depression in the metal at the aXial center oi" the rounded bottom, 8. lt'may, however, be formed in any other derab'le or convenient way, as for instance, bv riveting a short piece or' wire or nickel, platinum, or other suitable material, to the rounded bottom, 8, as will be understood by those skilled in the art.

17, 17 are holes in the wall of the ground terminal, 6, to admit'the explosivemixture to the spark gap. These holes may be or -which is adaptable to certain designs of spark plugs now in use.

ln order to show the adaptability of this construction, l have preferred to omit the metal body or shell which is customarily screwed into the wall of the explosive chamber, and show instead, in Fig. 4, the insulated electrode with its insulation and a modiied form ot my combined ground terminal and packing washer supported in a counterbored hole formed directly in the wall or the explosion chamber. li' desired, a metal body or shell of usual construction may be employed, and, in the usual construction of spark plugs with which l am familiar, it is necessary to employ such a member because it i'orms the ground terminal which carries the nominally` grounded naaaeor ,explosion chamber or cylinder of an internal combustion engine, and 19 is a hole through Ithe wall, 18. This hole is enlargedby counter boring from the outer. surface of the wall, 18, asv shown at 20, part waythrough the wall, 18. A. shoulder, 21, is thus formed in the metal surrounding, the hole, 19. The counterbored portion, 20, of the hole, 19, is internally threaded to receive a correspondinglythreaded clamping member, 22.

The insulation, 23, which carries the insulated electrode, 24, is formed similar to part 5 shown in Fig. 1, except that in order to maintain the necessary distance between the clamping member, 22, and the exposed, insulated electrode connections at the top oit the insulation, the lengthA of the insulation, 23, from the shoulder, 24, to the top end is made greater than the corresponding portion ot the insulation,5, shown in Fig. 1.

The combined ground terminal and packing washer which l prefer to use in connection -with the spark plug shown in Fig. 4 consists, as in the form shown in F ig. l, of a metal cylinder or thimble, 25, having a practically straight body portion, 26. lt, also, has an outwardly turned Harige, 27, at the top of the body portion, 26. lnstead of terminating at this flange, however, the metal is continued above it in the l'orm of an enlarged cylinder, 28, whichV extends to the shoulder, 24, of the insulation, 23, and is there inturned to form a second flange, 29, the purposes of which are to form a metal cushion between the end of the clamping member, 22, and the shoulder, 24, of the insulation, 23, and further to `form a means coperating with the shoulder, 24, for withdrawing the member, 25, with the insulation, 23, when it is desired to inspect or change the spark plug. Y

lln order to permit the flange, 29, to pass over the enlarged portion of the insulation,

23, below the shoulder, 24, ll prefer to cut the metal of the Harige, 29, and the enlargedcylinder, 28, longitudinally, as shown by the Slots, 30,- 30, thus forming outwardly yielding ungers, 30, 30f. After the insulation, 23, has been inserted into member, 25, these lingers close in and the flange, 29, overlaps the shoulder, 24a, for'4 the purposes set forth. lf desired, the slots, 30, 30, may

be omitted, and the member, 25, be secured to the insulation by forming the flange, 29,

after the insulation, 23, has been inserted into the ground terminal, 25. Such a construction, however, makes it diliicult to clean the insulation without deforming the ground terminal, and l prefer to employ the slotted form shown.-

ln Figs. 'l' and 8, a modied term 31, ot

my improved ground terminal and packing washer is shown. ln this form there is the straight cylindrical portion, 32, but the top end is simply liared outwardly to .form the iange, 33, and is not inturned as is the flange of the ground terminal shown in Figs. 1, 2 and 3,not turned upward to form an enlarged cylindrical body portion as shown in Figs. 4, 5 and 6. The sparking point, 34, of the ground terminal, 31, shown in Figs. 7, 8 and 9, is formed out of the metal of the bottom part of the straight cylindrical portion. Transverse slits or holes, 35, extending' part way around the circumference, are cut in the wall of the cylinder near the bottom end so as to leave transverse bars, 36, extending between the intervening portions of the wall. Spar-king points, 34, may be formed at the centers of these strips, 36, and the strips be bent inwardly until the sparking points stand approximately in the center of the cylinder, directly under the sparking point of the insulated electrode when the spark plug is assembled. ln this construction, the ground terminal must be made of material suitable for use as sparking points, or the sparking points must be separately made of suitable `material and attached to the strips, 36.

ln Fig. 9 is shownl a spark plug in which a ground terminal and packing washer such as is shown in Figs. 7 and 8 is used. ln addition to the flange, 33, however, there is shown in this arrangement, an additional washer, 37, of yielding material, such as is commonly used in'spark-plug construction. ln Fig..10' is shown an enlarged partial section through this packing washer arrangement.

, When the opposed surfaces of the shoulder, 38, on the insulation, 5, and the shoulder, 39, in the metal wall of the hole, 40, in

Awhich the spark plug elements are assembled, are'true and smooth, the comparatively soft metal of which the combined ground terminal and packing washer is madeis sufficient packing to make fluid tight joints, but when necessary, the additional Washer, 3 7, of yielding material may be used. it is to be noted particularly that the use of such an additional washer does not materially aect the vlength of the spark 'llhe combined ground terminal and packing washer may be made of any metal or other conducting material `found suitable. lt may be :tormed by pressing' or drawing it from sheet me. 11;' or, it may be formed from metal tubing; or, in any of the various other ways well known to metal workers and found convenient or desirable. lt may be made of copper or of German silver and the sparksof ing point be lmade of the same metal, or of n iron, nickel, platinum or'any other suitable metal.

inner and outer transverse shoulders, a metal shell adapted to be secured in the wall of the combustionchamber which the spark plug serves, a ground terminal provided with a sparking point at its inner end and an outwardly turned, transverse Harige at its outer end, the body portion of the ground terminal being adapted to enter the bore of the metal shell, and the Harige oi the ground terminal being adapted to rest on the outer end of the metal shell, and means cooperating with the insulation and the metal shell to clamp the Harige of the ground terminal between the inner shoulder on the insulation and the metal shell.

2. A- ground terminal for spark plugs, having a tubular body portion provided at its inner end with a sparking point and at its outer end with an outwardly projecting transverse Hange adapted to serve as a packing washer for the insulation which surrounds and carries the inner electrode, said Hange being formed by Hrst outwardly Han ing the end metal of the tubular body portion and then underturning the outer portion of the Harige thus `formed and including a washer of yieldin material between the uppeig, outwardly ired portion and the lower /underturned portion.

3. A ground terminal for spark plugs, having a tubular body portion provided with a Asparking point at its inner end, an outwardly turned transverse Hange at its outer end, a tubular extension to the outwardly turned transverse Harige, an inwardly turned transverse Harige at the outer end of the tubular extension., said outwardly turned transverse Harige being adapted to serve as a packing washer between a shoulder on the insulation which surrounds and carries the inner electrode and a shoulder on the wall of the supporting member, and the inwardly turned transverse Harige being adapted to serve as a cushioning washer between a shoulder on said insulation and the member which clamps it to the supporting member and to serve as a means for withdrawing the ground terminal with the insulation from the supporting member.

A. A ground terminal `for spark plugs,

nasen-sr having a tubular body portion provided with a sparking oint at its inner end, an outwardly turnedp transverse Harige at its outer end, a tubular extension to the outwardly turned transverse Harige, an inwardly turned transverse Harige at the outer end of the tubular extension, said outwardly turned transverse Harige being adapted to serve as a packing washer between a shoulder on the insulation which surrounds and. carries the inner electrode and a shoulder on the wall of the supporting member. and the inwardly turned transverse Hangs being adapted to serve as a cushioning washer between a shoulder on said insulation and the member which clamps it to the su porting member and vto serve as' a means or withdrawing the ground terminal with the insulation from the supporting member, the tubular extension and the inwardly turned transverse Harige being split longitudinally to permit the shoulders on the insulation to enter the tubular extension.

5. In a spark plug adapted to be secured in the opening in the wall of the combustion chamber which the spark plug serves, an insulation body surrounding and carrying the inner electrode and having an annular shoulder, a ground terminal carrying a sparking point at its inner end and an an nular Hangs at its outer end, a tubular member carried by the combustion chamber and provided with an annular shoulder, a coinpressible washer between said annular slioulder and said annular Harige on the ground terminal, and means for clamping said washer against said shoulder through themedium of said annular Hangs and the shoulder on the insulation body, the washer coming in direct Contact with the shoulder carried by the combustion chamber and the annular flange on the ground terminal coming in direct contact with the shoulder of the insulation body, whereby the compres-` sion of the washer in clamping the` parts in position will not vary the distance between the spark points1 y in testimony whereof l ax my signature in presence of two witnesses.

FRANK L. SESSIONS.

etv 

